[Tfug] MythTV hardware encoder advice

[John Gruenenfelder]

On Fri, Nov 13, 2015 at 01:55:09AM -0700, John Gruenenfelder wrote:
>
>Right now, I have *almost* everything working.  For some strange reason, the
>hue of the new recordings is slightly off making everything appear a little
>more green/yellow than it should.  I can correct this with the MythTV picture
>adjustments, but I'd like to find the root cause if I can.
>
>Also, I seem to be running into a bug with the MythTV internal player.  For
>some video formats (and I haven't yet nailed down exactly which ones are
>problematic), the internal player doesn't show anything.  It doesn't crash,
>but I get no video at all, just audio.  At first I thought it was a problem
>with my recording setup, but I found that playing the recordings back with an
>alternate player, like mplayer, worked fine.  Maybe it doesn't like the Radeon
>video card I put in there.  In the worst case, I'll just remove that and
>replace it with a simple video card known to work well in Linux.

Hey TFUG,

Just a quick update, on the off chance anybody is *really* interested...  :)

I managed to fix the two remaining issues I mentioned above.  The first, the
color problem, was what you might call a really really stupid mistake.  More
specifically, for the YCrCb component connection, the 'Cr' cable had come
loose and the picture was thus lacking a lot of color information.

The second issue was a little more nuanced.  MythTV supports numerous playback
methods.  The old motherboard had an old Intel chipset for the integrated
video, so I had MythTV configured to use the VAAPI acceleration setup.  The
new system has no integrated video so I put in my old Radeon HD 4850 GPU.  As
far as I can tell, the free radeon drivers should support VAAPI.  They don't
appear to *directly* support it, but rather support VDPAU and then that goes
through a VDPAU->VAAPI library.  For some reason, however, it wasn't working
correctly.

At first I thought I'd try the non-free fglrx driver, but it seems that the
support cutoff is now HD 5000 cards, so my 4850 is no longer supported.  I
didn't think it was *that* old.

Fortunately, MythTV also supports VDPAU directly, so I configured it to use
that and now my black screen video problems are gone.


If all those abbreviations have you confused, here is a brief public service:

Xv - original X Video acceleration architecture.  Accelerates scaling, color
   space conversions, and a few other things.
OpenGL - By mapping the video to a texture, it is possible to use generic
   OpenGL support to accelerate scaling, color space conversion, blending, and
   some other operations.
VDPAU - Nvidia's acceleration API.  Builds on Xv by supporting modern codecs
   like H.264, DivX, and MPEG4.  Accelerates parts of the actual decoding of
   some codecs; parts like the cosine transforms and such.
VAAPI - Video Acceleration API created by Intel.  Though originally for
   Intel's GPUs, they quickly open sourced it with the intention that it
   become the defacto *nix standard for video acceleration.  Despite the
   roundabout way in which the free radeon driver supports it, it does seem to
   have wider support than VDPAU currently.  VAAPI and VDPAU appear to more or
   less support the same operations.


-- 
--John Gruenenfelder    Systems Manager, MKS Imaging Technology, LLC.
Try Weasel Reader for PalmOS  --  http://weaselreader.org
"This is the most fun I've had without being drenched in the blood
of my enemies!"
        --Sam of Sam & Max
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